This is an application for a K23 award for Nirav Bhakta, MD, PhD, a postdoctoral fellow in pulmonary medicine at the University of California, San Francisco. Dr. Bhakta is beginning a career as a young investigator in translational research in asthma. Asthma is a chronic inflammatory disease of the airways in the lungs that leads to recurrent episodes of wheezing, cough and shortness of breath. There has been a dramatic increase in the prevalence, morbidity, and economic burden associated with asthma over the past 40 years. This K23 award will provide Dr. Bhakta with the support necessary to accomplish the following goals: (1) to develop an independent patient-centered translational research career focused on airway diseases; (2) to advance the application of multi-color flow cytometry to human tissue samples to quantitatively evaluate inflammatory pathways; (3) develop expertise in using airway epithelial cells in culture as a model system to interpret human data; and (4) to apply advanced biostatistical methods to the development of biomarkers to predict response to molecularly-targeted therapies. To achieve these goals, Dr. Bhakta has assembled a mentoring team comprised of a primary mentor, Dr. Prescott Woodruff, an expert in translational asthma research and molecular phenotyping of asthma; a co-mentor, Dr. John Fahy, an expert in translational asthma research and airway epithelial cell biology; and 4 grant advisory committee members: Dr. Mark Ansel, an immunologist with expertise in immune cell subsets and multi-color flow-cytometry; Dr. Dean Sheppard, a senior researcher studying inflammatory pathways in mouse models of asthma; and Dr. David Erle, an expert in the application of high-throughput technologies and statistical methods to study gene networks in asthma; and Dr. Mark Segal, a senior biostatistician with extensive experience in high-throughput data analysis. There is growing recognition that asthma is not a single disease, but rather has many different forms leading to variability in severity and response to medications between patients. It is likely that these differences are driven by the predominance of distinct underlying pathways of inflammation, the discovery of which would inform the development of novel targeted therapies. Identification of one such pathway, inflammation driven by T helper 2 (Th2) cells, has led to a novel blood biomarker (periostin) which predicts response to Th2-targeted therapy, proving the concept that molecular phenotyping can guide cytokine-targeted therapies. However, Th2 inflammation explains only a subset of asthma, and there is a need to identify other pathways, especially for the 10% of asthmatics who are severe and do not respond to standard therapies. The proposed research will investigate the role of one such pathway, inflammation driven by IL-17 cytokines, which preliminary findings lead us to hypothesize is associated with heightened eosinophilic inflammation and two cardinal features of severe asthma: excessive airway narrowing and mucous overproduction. An ongoing bronchoscopy study in severe asthmatics will be leveraged to obtain airway washings and tissues to test these hypotheses. The numbers of IL-17 cytokine- expressing cells will be assessed in these tissues with flow cytometry and microscopic examination, and their association with inflammatory cells, clinical airway narrowing, and mucous overproduction determined. Importantly, the proposed study will combine this data with experiments on isolated cells to develop biomarkers in the blood and sputum that reflect IL-17-driven inflammation in the lung. These biomarkers have the potential to improve asthma care by providing a test to identify the individuals most likely to respond to IL-17-targeted drugs already in development by pharmaceutical companies.